Research Of The Variation Law Between Heat Transfer Capacity And Resistance Of Tube-fin Heat Exchanger

Against the backdrop of the increasing abundance of human activities and the improvement of productivity,the conflict between human’s exponentially expanding consumption demand for material and energy and human energy supply is deepening.At present,the modern production widely uses a tube fin heat exchanger（T&F HX）.With the increasing energy crisis worldwide,improving the performance of tube fin heat exchangers has become the latest research goal for many scholars in related fields.Through reading a large number of references,I found that few scholars have studied the change law between heat exchange ability and resistance of tube fin heat exchangers.Therefore,it is of great significance to study the change law between heat exchange ability and resistance of tube fin heat exchangers.Firstly,this paper lists the fundamental equations including heat transfer calculation,coefficient of heat transfer,coefficient of convective heat transfer,etc.,which provide theoretical support for the subsequent thermodynamic calculation and numerical simulation.Secondly,the author develops the numerical models for light pipe,extended-surface tube,annular finned tube,and double H-type finned tube heat exchanger.Through thermodynamic calculation and range analysis,the structural parameters that have the greatest influence on the heat exchange ability and internal resistance of heat exchangers are studied.Analysis of the results shows that the structure that has the greatest impact on the heat transfer capacity in the light pipe and extended-surface tube heat exchangers is the outside diameter.The structure that has the greatest impact on the heat transfer ability in the annular finned tube and double H-shaped finned tube heat exchangers is the rib diameter and rib height.However,among the heat exchangers mentioned above,the structures that have the greatest influence on the interior are outside diameter,fin height,fin diameter and fin side length.Thirdly,by fitting the data of heat transfer factor and friction factor of various heat exchangers,the analysis of the fitted curves shows that the changes of heat transfer factor and friction factor of light pipe heat exchanger,extended-surface finned tube heat exchanger and various ribbed tube heat exchangers show a positive correlation.At the same time,under the same heat exchange capacity,the gas side resistance of the finned tube heat exchanger is the smallest,followed by the light pipe heat exchanger,and the gas side resistance of extended-surface finned tube heat exchanger is the largest.Further analysis shows that it forms a unified fitted equation between the heat transfer factor and friction factor of the annular finned tube and double H-shaped finned tube heat exchanger.The fitting relations between the heat transfer factor and friction factor of the light pipe,extended-surface tube,finned tube exchangers are respectively f=0.01477 j-0.05979,f=1.336′10^-4j^2.88917,and f=0.00991 j-0.04322,and the applicable ranges are 12.8￡j￡16.8,9.7￡j￡12.5 and8.0￡j￡15.7 respectively,with the maximum errors of 7.81%,24.49%and 16.06%and R2of 0.865,0.908 and 0.995 respectively.Finally,the author designs a triangular finned tube heat exchanger.Through numerical simulation,people can investigate the range of applicability of the fitted relationship between heat transfer factor and friction factor of finned tube heat exchanger.Analysis of the simulation results shows that the variation of fin edge length and fin pitch causes a positively correlated change in the relationship between heat transfer factor and friction factor for the triangular finned tube heat exchanger.At the same time,this change is consistent with the variation law between heat transfer factor and friction factor of circular/double H-shaped finned tube heat exchanger.Comparing the heat transfer factor and friction factor of the triangular finned tube heat exchanger with the finned tube heat exchanger fitted equation,the fitted equation is applicable to the circular and double-H finned tube heat exchanger.In addition,it also applicable to the triangular finned tube heat exchanger,which expands the application of the above fitted equation to some extent.